1. Field of the Invention
The present invention generally relates to an apparatus and method for inverse telecine and video de-interlacing, and, more particularly, to a cadence detection system and method that is programmable to improve picture quality of broadcasted videos with mixed video and film mode sources in TV and set-top-box (STB) products.
2. Relevant Background
Interlaced video was used for cathode ray tube (CRT) displays and is found throughout a number of broadcasting formats. Modern video displays, e.g., liquid crystal displays (LCD) and plasma displays, do not operate in interlaced mode. Therefore, de-interlacing circuitry is needed in set-top-box (STB)/TV to de-interlace video into progressive video that can be played on modern video displays.
Currently, there are a number of different source formats. Video formats usually display at 50 or 60 frames per second; film formats are commonly captured at 24 or 25 frames per second. Because of the difference in frame rate, telecine is applied to a film source video in order to properly display the film source video on a video display. Reverse telecine may be applied to the telecined film source video to recover a higher quality non-interlaced video to display on a compatible device, such as a modern video display.
Cadence detection involves finding the source format of a sequence of video fields or detects the absence of motion between frames (still pictures) and determines whether a video is originally from a video or film source that had interlacing or telecine applied. De-interlacing or inverse telecine can be appropriately applied to the video after cadence detection in order to remove the selected filtering.
Mixed video and film sources are commonly seen in broadcasted videos, e.g., graphics overlap over video or scrolling text on a film-source video. A global film mode detection and global switching between inverse telecine and video de-interlacing mode is suboptimal in this case as it would leave either compromised vertical resolution or unhandled feathering/comb artifacts on the part of the unremoved interlace or telecine filtering.
U.S. Patent Publication No. 2007/0291169, “Region-Based Cadence Detector,” discusses blocked based film/video decision and switching. A frame is segmented into a pre-set number of regions (or clusters of blocks) for cadence and phase tracking. A block level inverse telecine or video de-interlacing is applied to the mixed source video. However, region-based cadence detection suffers in picture quality and robustness due to artifacts from the switching.
Accordingly, there is a need in the art for increasing detection accuracy to prevent feather/comb artifacts on moving video object areas and increasing robustness of film and video mode detection to improve picture quality of mixed cadence sources.